The points were safe when Armand Traore took advantage of some indecisive defending from Tommy Smith - before the Town centre-back atoned slightly with a wonderfully acrobatic consolation goal as the game headed into injury time.
An intriguing, rather than enthralling, first 15 minutes saw both promotion hopefuls size each other up with Town top scorer David McGoldrick the first to test the target but seeing his 25-yard shot fly just too high.
The game burst into life on 24 minutes when Luke Chambers ghosted into the box but was denied by a great save by Rob Green.
A goalmouth scramble saw a grounded Chambers hook the ball across but Joey Barton hacked clear from Paul Taylor.
In the 33rd minute, QPR had their own gilt-edged chance when Kranjcar and O'Neil combined to tee up Charlie Austin but the striker's header from four yards was brilliantly tipped over by Dean Gerken.
Austin was then denied a goalscoring opportunity by a brilliant last-ditch tackle from Christophe Berra after indecision from Ipswich in clearing Richard Dunne's hopeful punt.
QPR continued to cause problems in the Town area with Chambers hacking the ball clear from his own goal line before Paul Anderson' 30-yard shot at the other end was saved by Green at the second attempt.
The second half started with Paul Taylor testing Green's handling from distance before the visitors took the lead seven minutes after the restart. Kranjcar ghosted past Chambers and Taylor before calmly slotting the ball into the far corner.
The goal settled QPR down and they began to take control. A second goal looked likely and it duly followed in the 66th minute when Austin was afforded time to shoot from 25 yards and Gerken could only parry his effort to the feet of O'Neil who gobbled up the rebound.
With 15 minutes left, the game was over when Smith's poor attempts to deal with Clint Hill's long clearance allowed Traore to nip in and push the ball past Gerken into the corner.
Town were struggling to find a response until the 90th minute when Smith met Stephen Hunt's corner with a wonderful bicycle kick which flew into the corner for the goal of the game.
It mattered little as Ipswich slipped out of the top six while QPR remain hot on the heels of Leicester and Burnley.
- Sports & Recreation
- Niko Kranjcar
- Luke Chambers
- Armand Traore